Sharing some experience relating to the Hughes Airgap intake I'm currently working on. The only thing that didn't go wrong was coolant leaking. Everything else though,,,,,,,

First, do NOT use any RTV on the intake manifold gasket anywhere. I did use a little smeared on the flats and around the cooling ports. This has allowed huge leaks into the the intake chambers, to the point of pooling oil at the valves. I suspect fuel has also made it's way into the crankcase as the oil is black with only 250 or so miles. I've yet decided on how best to get it out of the intake port,,,,,

Secondly, and this may or may not be related to the use of RTV, do NOT use Reinz front/rear gaskets. I only have 250 miles on this motor re-build and they are completely disintegrated. Oil from the gallery was blowing out the rear of the motor and pooling in the pockets next to the trans bellhousing bolts. These are the ones that ship with the Hughes Airgap.

I'll be putting Fel Pro gaskets back in this time - dry.

 

I noticed something about the front rear gaskets. From the factory they put LOTS of RTV on them and there are little "nipples" on the gaskets that need to go completely into the block surface. The block has holes for them. I spent 30 minutes digging old RTV out of the holes with a thin drill bit so the gaskets could go in properly and seat perfect.

THat was probably the problem, unless you swear you did that. I used the reinz gaskets.

 

I used the Reinz gaskets too, stock manifold. No problems that I'm aware of over the last 20k miles. Hope I don't have problems, you're making me paranoid now.

 

I think it was your installation technique. When I installed my airgap, I used RTV on the coolant ports and ultra black rtv on the end seals ans I have no leaks.

 

you shouldnt be using RTV on intake manifold gaskets, if you want to put anything on there use spray tack. Don't use the front and rear rubber gaskets, use a bead of rtv silicone and put about a 1/2in or so gob in the corners where the intake gaskets meet the block. If you look up an Edelbrock Air Gap on summit look at the instructions it say not to use the rubber gaskets for the front and back of the block. I found this out after a couple gasket failures on my Small block chevy Air Gap, which was a failure to read instructions. Who reads instructions come on?? haha I have installed the Air Gap now on my 360 also, no leaks the first go at it from learning my lesson on my small block chevy. Set the intake manifold down dry on the engine with out the gaskets and you'll see how much nicer it fits together.

 

I know of a lot of engine builders that use a smear of rtv around the coolant ports. So what wrong with that? As long as it's not in contact with gas it's fine.

 

I've also read where RTV is discouraged.. but, screw them.. I put a light bead around each port, CLOSE to the coolant ports on the head, and allowed it to cure.. I ran a light bead on the manifolds port a little further away from the port than on the head side..

the cross block dowel gaskets can be a PITA.. the set I got with the A-G were bent to hell and back, so I didn't even try.. A set of Fel-Pro's had wobbled dowels right out of the sleeve.. So, I swapped them for ones that had good dowels..

clean surfaces is the name of the game imHo.. and consistent beads.. also, more should be shared in the instructions on the sequence of laying in those gaskets.. it should be:

with gaskets, copper RTV, bolts, a plastic 'razor' scraper, a bottle of alcohol, and lint free towels... go:

- clean the hades out of the mating surfaces.. scrape them clean, very clean.. scrub them with alcohol, allow to dry.. try not to touch them with oily/greasy fingers..

- lay a nice decently thick bead in the cross block area, and in such a way that the bead fits into the little groove on the cross block dowel gaskets..

- lay a fine bead around the heads coolant ports.. allow to cure about 70% or so (a touch tacky, but mostly set)

- lay a fine bead around the manifolds coolant ports, with a large enough loop that will encompass the inner bead on the head (space, when compressed, may be at a premium, so it would be good to not create a ridge of RTV- the idea is having a small enough bead that it will be able to smoosh flat, and the edges of the smooshed flat rtv won't overlap the edges of the other side- so the gaskets sit flat as possible)

- lay a healthy bead across the manifold that will be directly above the cross block dowel gaskets..

- place the head mating surface gaskets on the heads..

- put a blob of RTV in the corners where the runner gaskets meet the tabs of your head gaskets..

- place the cross block dowel gaskets where they go, and seat them over the top of the runner gaskets (it is a very small 'overhang')..

- put headless bolts in each corner (cut the heads off the previously used, and spent, tty bolts)

- put the manifold STRAIGHT down on the heads..

- Start your torquing sequence..

RTV is good stuff when used correctly, it's been my experience.. the trick is to lay a CONSISTENT bead.. you want one, steady, unbroken and uniform sized bead.. breaks in the bead create an area that is weak, and will give pressure something to push against that 'gives'.. It may not even break the bead at first, but it can push it out of the way enough to allow a leak.. at that point, it's like the little dutch boy standing at the dam with his finger plugging a hole.. it will spread, and you'll leak..

The cross block dowel gaskets aren't under any real pressure.. if you install them correctly, RTV them top and bottom, on a clean surface and allow them to cure before firing up the engine, chances are they won't leak.. like, ever..

 

Agree that rtv around coolant ports is good, in fact that's the only thing that prevented a coolant leak into the crank. I followed a suggestion by a published engine builder to smear a thin layer on the large flat between banks of intakes to hold the gasket in place. It was this plus what seems to be a possible issue with the metal / rubber front rear gaskets that has got me hosed.

I did go look at the Edelbrock instructions as DodgetheDad suggested,and they do recommend using rtv beads only front and rear instead of the metal/rubber gasket. Seeing what happened to mine, the front/rear rtv seems like a good idea.

 

drew,,you da man. I sure haven't seen any instructions like this

To pick your brain some more - how would you go about clearing out the head intakes to get them clean again? Without pulling the heads that is,,,,,

 

debris? a vacuum and one of those corner attachment thingies cut down to the size of a pencil..

carbon build up? acetone, toothbrush, lint free shop towels, and the vacuum.. and allowed to dry completely..